The invention relates to high pressure thrust bearing assemblies and, more particularly, to the arrangement of a plurality of stiff spring subassemblies in such a thrust bearing to provide flexible mounting for a plurality of bearing thrust plates that are positioned to support a bearing ring for rotation.
Long before the present invention it was generally well-known that frusto-conical spring discs are useful in providing a relatively stiff, resilient force capable of supporting heavy loading with a uniform resilient stiffness. Such spring discs have come to be called Belleville spring discs since the issuance of U.S. Pat. No. 75,970 to Mr. Belleville in which he disclosed the so-called Belleville spring. Over the years a plurality of different spring assemblies have been developed to more efficiently utilize Belleville spring discs. For example, such spring discs have been stacked in concentric, parallel relation as explained in U.S. Pat. No. 3,029,071 issued to J. Wells. And Belleville spring discs have been stacked in coaxial relationship with centering rings and retainer flanges disposed around their respective inner and outer abutting peripheral surfaces to maintain concentricity of the discs and to counteract the hysteresis problems that cause some Belleville spring systems to be faulty or non-uniform in operation. One example of such retainer rings and supporting flanges used with a Belleville spring assembly is shown in U.S. Pat. No. 3,873,079 to S. Kuus.
In addition to the various prior art improvements in Belleville spring assemblies, per se, the use of Belleville springs in a wide spectrum of different applications has occurred. In general, so far as the present applicant knows, such prior applications have been limited to relatively light loading on the springs where considerable movement or vibration is induced in the spring by the load. An example of such a vibration dampening shock mount utilizing a Belleville-type spring is shown in U.S. Pat. No. 3,113,755 issued to Stevens et al. At the other end of the loading spectrum stiff Belleville spring assemblies have been used to support heavy, relatively static loads as explained in U.S. Pat. Nos. 2,191,901 and 2,708,110 which describe the use of such springs for supporting heavy loads where little movement on the spring is anticipated in normal use of the system.
Despite the general familiarity of those skilled in the high pressure thrust bearing art with Belleville spring arrangements and their advantages, it continues to be common practice to rely on conventional coil spring subassemblies to support flexibly movable thrust bearing plates in high pressure thrust bearing applications, despite the fact that the pressure has steadily increased from the early 1920's to the present time. This increasing pressure on thrust bearings has been observed, for example, in the evolution of the type waterwheel-driven electric generators that are commonly supported in rotating relationship by such bearings. In order to accommodate these increases in pressure, tighter packing of coil spring subassemblies has been resorted to in order to adequately support the thrust bearing plates in such bearing assemblies without exceeding predetermined overall dimensions for the bearing assembly. However, at the present time the existing space limitations and requirements of low friction losses for thrust bearings in larger waterwheel generator installations requires that stiffer spring subassemblies than any heretofore employed be developed for these applications. Moreover, in order to provide desired load distribution on the bottom surfaces of flexible thrust plates for such high pressure thrust bearings it is desirable to utilize stiff spring subassemblies that can have their stiffness readily modified without changing their exterior dimensions. The present invention provides the necessary spring stiffness and easy adjustment of individual spring subassembly stiffness to accommodate substantial anticipated increases in thrust bearing pressures. As explained in detail below such increased pressures are typically applied from a rotatable bearing runner ring that transmits thrust load from a generator shaft to flexible thrust plates supported by a plurality of such spring subassemblies in a thrust bearing made according to the invention.